Setting the perfect white balance while rendering has always been a tricky affair. What makes it even more difficult is our own aesthetic perception. Should it look a bit more cool or warm? This is what happens when you try to set it manually by eye. Judging your own eyes becomes a bit deceiving. You’re never sure if you’ve gotten the white balance correct or not. So before I tell you the secret of getting a great white balance, let us discuss what exactly is white balance.
White balance is a photographic term that aims to remove any color cast or tint from your photos. The objective is to make sure that what looks white in real life, also gets rendered as that same white in the photo. All digital cameras have an auto white balance feature, and you can bet even they’re not that good at their job. Incorrect white balance introduces a color tint, usually blue or yellow, to your images. The controls for this feature work by selecting that color tint which we wish to remove from our image. Presently, VRay doesn’t have any automatic setting to calculate this for you. So what can we do to remove all the hassles and set a perfect white balance in VRay?
The answer lies in doing what real photographers do to solve this problem.
A while back I came upon this solution presented in the book named Digital Lighting and Rendering by Jeremy Birn. Discussed within this book, was a technique involving the use of perfectly white or grey balls, photographed in the same environment, to be used as a reference.
The principle behind this technique is to identify areas in your image that are supposed to look precisely white or grey, then using those areas as reference for the tint removal process. Based on this same principle, there are a variety of techniques that accomplish the same task, but this method is by far the easiest and effective.
White Balance Solution
- Render your main scene as just a preview. You can simply use the light cache for this purpose.
- Find a spot in the middle of the scene which is being softly lit without being hit by direct light. Medium ambient light serves well for this purpose.
- Place a pure white sphere in that spot. A good size for the sphere would be 10-20% of the image frame size.
- Render this change as a preview again.
- Set the white balance setting for your VRay Physical Camera to Custom, and bring its color selector probe over the sphere.
- If the colors on the sphere are tinted, then choose the color from a portion with a low saturation of that tint for best results.
- Using this subtle tint as correction, you’ll be able to remove the color cast from your entire scene.
Alternatively, you can even use white balance as a creative tool to make filter effects like midnight blue or noon yellow. This can help you to achieve deep blue night skies or a hot noon sun.
As for the rendering settings, I’ve used exponential color mapping with the Irradiance Map / Light Cache combination for global illumination. Setting IM preset to Low and LC subdivs to 500 is enough for trying out this method.
Make sure your display is correctly calibrated to a standard 6500k color temperature. You don’t want any blue or yellow tint to your screen. Otherwise, this will adversely affect your white balance.
If you found this tip helpful, you can be sure to find plenty more on my site. And like always, don’t forget to comment and share your views with me. Talk to you later, guys.
